docs: def get_river_index(self, river_id):
          """
          This method retrieves the river index in the netCDF
          dataset corresponding to the river ID.
  
          Parameters
          ----------
          river_id: int
              The ID of the river segment.
  
          Returns
          -------
          int:
              The index of the river ID's in the file.
  
  
          Example::
  
              from RAPIDpy import RAPIDDataset
  
              path_to_rapid_qout = '/path/to/Qout.nc'
              river_id = 53458
  
              with RAPIDDataset(path_to_rapid_qout) as qout_nc:
                  river_index = qout_nc.get_river_index(river_id)
  
          """
          try:
              return np.where(self.get_river_id_array() == river_id)[0][0]
          except IndexError:
              raise IndexError("ERROR: River ID {0} not found in dataset "
                               "...".format(river_id))